Inverse variation formula is y = k/x To find k you would multiply by x on both sides. So..xy = k Since k is a CONSTANT we need to multiply xy and get the same number (k). This only happens with the last choice. Each pair of numbers yields, 60. 2*30 = 60; 3*20 = 60, 4*15 = 60; 5*12 = 60
